Let parent handle invalidation of RenderText

Instead of letting invalidateTreeIfNeeded() work for RenderText,
this CL let RenderText's parent handle invalidation of RenderText
during invalidateTreeIfNeeded().

This avoids the complexity of implementing a correct and efficient
RenderText::clippedOverflowRectForPaintInvalidation(), and I believe
the performance is also better than full-functional RenderText
invalidation.

BUG=394133,409068

Review URL: https://codereview.chromium.org/496923005

git-svn-id: svn://svn.chromium.org/blink/trunk@182069 bbb929c8-8fbe-4397-9dbb-9b2b20218538